Shorebird and Waterfowl Monitoring Research

In Biological Monitoring, Bird Monitoring, Birds, Research by Administrator

Past shorebirds and waterfowl monitoring in and around Elkhorn Slough (1989-2000)
Over the last several decades, various shorebird and waterfowl monitoring has been carried in and around Elkhorn Slough. From 1989-2000, for example, Sue Shaw faithfully recorded all shorebird and waterfowl seen during her regular visits to measure water quality at 24 stations. The stations were located along the entire length of the slough from the mouth at Moss Landing and adjacent areas all way up to the head of the slough, as well as farther south at Salinas River, Moro Cojo, and nearby locations. The data show that diversity and abundance of shorebirds and waterfowl at Elkhorn Slough and environs have remained relatively stable during that decade. Overall, a total of 29 different types of birds were recorded, and more commonly seen birds included loons, cormorants, pelicans, gulls, terns, shorebirds, herons, egrets, ducks, geese, coots, grebes, and kingfishers. Abundance of many individual bird groups (e.g. gulls, terns, cormorants, Great Blue Herons, egrets, and geese) also remained unchanged. In contrast, the 24 stations differ significantly in the relative abundance and occurrence of species creating characteristic bird faunas. Salinas River Lagoon took top honors with a mean annual total of nearly 9000 birds, most of which were gulls (7000) and pelicans (800)! The sites with the highest diversity were Jetty Rd. and North Potrero, each supporting more than 12 types of birds (including loons, cormorants, pelicans, gulls, terns, shorebirds, herons, egrets, ducks, geese, coots, grebes, and kingfishers).

Present Shorebird and Waterfowl Monitoring on the Reserve (2001-present)

An ongoing project, began in 2001, is the volunteer-based survey along the South Marsh trail. Birders carry out monthly surveys of shorebirds and waterfowl at low tide during 10 minute watches in five defined areas of Reserve wetlands (mudflats and ephemeral freshwater habitats) located along the South Marsh loop trail: Barn Pond (the seasonally wet area below the barns), Big Lagoon and 5-Pans (the tidal areas separated by the causeway), Freshwater Rookery (the seasonally wet pond adjacent to the rookery and Tidal Rookery (the tidal area on the west side of the berm that connects to Big Lagoon towards the west). The goal of this program is to quantify the diversity (species richness) and abundance of shorebirds and waterfowl using central Reserve wetland habitats. If dramatic changes are detected, we can contact other organizations and reserves along the Pacific coast and attempt to find the cause of the pattern, if it is widespread. If the change is only local, we can seek explanations in terms small-scale events such as alterations to pollution levels or habitat management strategies.

Results include data pooled from 2001 – 2008 unless otherwise noted (click to view associated figures 49KB / PDF). Diversity (number of species) and abundance varied significantly by site (P<0.0001), but not by year (P>0.05); 2004 and 2005 were excluded due to insufficient data. A total of 60 species was observed during the course of observation. 5-Pans and Big Lagoon had the greatest diversity (50 and 46 species, respectively). Tidal Rookery had 39 species, while Freshwater Rookery and Barn Pond had the lowest diversity (25 and 22 species, respectively). Total abundance was greatest at Big Lagoon (nearly 18,000 birds, or 46% of all birds counted), followed by 5-pans and Tidal Rookery, each with over 8,000 birds (20% per site); Barn Pond and Freshwater Rookery each had approximately 2000 birds (7% per site).

In terms of abundance of individual species, Least and Western Sandpipers (species combined) tallied an amazing 15,127 birds, followed by Willets (4449 birds), Marbled Godwits (2583 birds), Short and Long-billed Dowitchers (species combined) (1966 birds), Snowy Egrets (1144 birds), Bufflehead (991 birds), Western Gulls (827 birds), and Great Egrets (758 birds). Combining all sites and years revealed that shorebirds were the most abundant group, with 26,260 birds, followed by waterfowl (over 7,000 birds), and herons and egrets (over 2000 birds).